1. Technical Field
The invention is related to electrostatic lenses or mass energy filters for charged particles of the type employed in laboratory instruments for surface analysis, such as electron microscopes and spectrometers, employed on spacecraft for analyzing charged particles, for example.
2. Background Art
Electrostatic lenses for charged particle optics are usually bulky but of fairly simple shape and that have to be machined with stringent tolerances. Fundamental limitations such as spherical aberrations result in lens diameters much larger than the useful beam width, particularly, for example, in electron microscopy. There are, however, a number of applications where the size of electrostatic lenses could be reduced significantly without loss of performance. One area of special interest is the mass and energy detection of ions and electrons. In the general context of building more compact laboratory instruments or of building smaller scientific payloads for spacecraft, the reduction of mass, volume and power is greatly needed. However, the signal level of microscopes, telescopes and detectors is usually proportional to the acceptance area of the instrument and hence it is desireable to have the acceptance area large in order to collect as much signal as possible.